Step 1: The question asks how often the injectable contraceptive DMPA must be repeated.
Step 2: DMPA stands for Depot medroxyprogesterone acetate, a progestin-only agent injected deep into muscle as an oily depot. The depot slowly leaks the hormone into the blood, keeping levels high enough to block ovulation for roughly three months.
Step 3: The recommended schedule is 150 mg every 3 months (about 12 weeks). This makes the 3-month answer correct.
Step 4: Other injectables differ: norethisterone enanthate is repeated every 2 months and combined monthly injectables every month, so 6 months, 9 months and 45 days do not fit DMPA.
\[\boxed{3\ months}\]